Modified pigments and process for preparing modified pigments

ABSTRACT

Processes for preparing modified pigments are described. In one embodiment, the process comprises the step of combining, in any order, a pigment having attached an electrophilic group and a thiol reagent comprising at least one —SH group and at least two ionic or ionizable groups. In a second embodiment, the process comprises the step of combining, in any order, a pigment having attached an electrophilic group and a thiopolymer comprising at least one —H group. Modified pigments are also described.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of prior U.S. patentapplication Ser. No. 10/142,596, filed on May 10, 2002 now U.S. Pat. No.6,833,026.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to modified pigments and to processes forpreparing modified pigments.

2. Description of the Related Art

The surface of pigments contain a variety of different functionalgroups, and the types of groups present depend on the specific class ofpigment. Several methods have been developed for grafting materials and,in particular, polymers to the surface of these pigments. For example,it has been shown that polymers can be attached to carbon blackscontaining surface groups such as phenols and carboxyl groups. However,methods which rely on the inherent functionality of a pigment's surfacecannot be applied generally because not all pigments have the samespecific functional groups.

Methods for the preparation of modified pigment products have also beendeveloped which can provide a pigment with a variety of differentattached functional groups. For example, U.S. Pat. No. 5,851,280discloses methods for the attachment of organic groups, such as ionic orionizable groups, onto pigments including, for example, attachment via adiazonium reaction wherein the organic group is part of the diazoniumsalt. The resulting surface-modified pigments can be used in a varietyof applications, such as inks, inkjet inks, coatings, toners, plastics,rubbers, and the like.

Other methods to prepare modified pigments have also been described. Forexample, PCT Publication No. WO 01/51566 discloses methods of making amodified pigment by reacting a first chemical group and a secondchemical group to form a pigment having attached a third chemical group.Ink compositions containing these pigments are also described.

While these methods provide modified pigments having attached groups,there remains a need for improved modified pigments as well as forprocesses for attaching groups and, in particular, polymeric groups, toa pigment. These additional methods may provide advantageous productsand alternatives for forming modified pigments.

SUMMARY OF THE INVENTION

The present invention relates to processes for preparing modifiedpigments. In one embodiment, the process comprises the step of:combining, in any order, a pigment having attached an electrophilicgroup and a thiol reagent comprising at least one —SH group and at leasttwo ionic or ionizable groups. Preferably the thiol reagent is analkylthiol substituted with at least two carboxylic acid groups. In asecond embodiment, the process comprises the step of: combining, in anyorder, a pigment having attached an electrophilic group and athiopolymer comprising at least one —SH group and at least one ionic orionizable group. Preferably the thiopolymer comprises the reactionproduct of a polymer having at least one anhydride, at least oneactivated carboxylic acid, or at least one carboxylic acid or saltthereof; an aminoalkane thiol or an aromatic amino thiol; and optionallyan activating agent.

The present invention further relates to modified pigments. In oneembodiment, the modified pigment comprises a pigment having attached agroup comprising the formula —S—[PI]. In a second embodiment, themodified pigment comprises a pigment having attached a group comprisingthe formula —X-Sp-S—[PI], wherein X is an arylene, heteroarylene, oralkylene group, Sp is a spacer group. For both embodiments, PIrepresents an organic group substituted with at least two ionic orionizable groups or a polymeric group comprising at least one ionic orionizable group.

The present invention further relates to ink compositions, in particularinkjet ink compositions, comprising the modified pigments describedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the effect of the targeted percent ofanhydrides reacted with aminoethane thiol (AET) on the expected acidnumber of the resulting product for several styrene-maleic anhydridepolymers.

FIG. 2 is a graph showing the effect of the targeted percent ofanhydrides reacted with aminoethane thiol (AET) on the expectedmolecular weight of the resulting product for several styrene-maleicanhydride polymers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to processes for preparing modifiedpigment products as well as to the modified pigment products themselves.

In the process of the present invention, a pigment having attached anelectrophilic group is combined with an SH-containing compound. Thepigment can be any type of pigment conventionally used by those skilledin the art, such as black pigments and other colored pigments.Preferably, when the pigment is a black pigment, the pigment is carbonblack. Mixtures of different pigments can also be used. These pigmentscan also be used in combination with a variety of different types ofdispersants in order to form stable dispersions and inks.

Representative examples of black pigments include various carbon blacks(Pigment Black 7) such as channel blacks, furnace blacks and lampblacks, and include, for example, carbon blacks sold under the Regal®,Black Pearls®, Elftex®, Monarch®, Mogul®, and Vulcan® trademarksavailable from Cabot Corporation (such as Black Pearls® 2000, BlackPearls® 1400, Black Pearls® 1300, Black Pearls® 1100, Black Pearls®1000, Black Pearls® 900, Black Pearls® 880, Black Pearls® 800, BlackPearls® 700, Black Pearls® L, Elftex® 8, Monarch® 1400, Monarch® 1300,Monarch® 1100, Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800,Monarch® 700, Mogul® L, Regal® 330, Regal® 400, Vulcan® P).

The pigment may also be chosen from a wide range of conventional coloredpigments. The colored pigment can be blue, brown, cyan, green, white,violet, magenta, red, orange, yellow, as well as mixtures thereof.Suitable classes of colored pigments include, for example,anthraquinones, phthalocyanine blues, phthalocyanine greens, diazos,monoazos, pyranthrones, perylenes, heterocyclic yellows, quinacridones,and (thio)indigoids. Such pigments are commercially available in eitherpowder or press cake form from a number of sources including, BASFCorporation, Engelhard Corporation and Sun Chemical Corporation.Examples of other suitable colored pigments are described in the ColourIndex, 3rd edition (The Society of Dyers and Colourists, 1982).

The pigment can have a wide range of BET surface areas, as measured bynitrogen adsorption. It is well recognized by those skilled in the artthat the pigment may be subject to conventional size reduction orcomminution techniques, such as ball or jet milling, to reduce thepigment to a smaller particle size, if desired.

The electrophilic group of the pigment used in the process of thepresent invention comprises any group capable of reacting with amaterial having at least one thiol group. Thus, for example, theelectrophilic group may comprise a carboxylic acid or ester, anactivated carboxylic acid, an acid chloride, a sulfonyl chloride, anacyl azide, an isocyanate, a ketone, an aldehyde, an anhydride, anα,β-unsaturated ketone, aldehyde, or sulfone, an alkyl halide, anepoxide, an alkyl sulfonate or sulfate, a triazene, or salts andderivatives thereof. Preferably, the electrophilic group is anα,β-unsaturated ketone, aldehyde, or sulfone group or an alkylsulfategroup or salt thereof. For example, the electrophilic group may be a2-(sulfatoethyl) sulfone group or a salt thereof.

The pigment having attached an electrophilic group can be prepared usingmethods known to those skilled in the art. For example, these pigmentscan be prepared using the methods described in U.S. Pat. Nos. 5,851,280,5,698,016, 5,922,118, and 5,837,045, and PCT Publication Nos. WO99/51690 and WO 00/22051, the descriptions of which are fullyincorporated herein by reference. These methods provide for a morestable attachment of the groups onto the pigment compared to traditionaladsorbed groups, such as polymers, surfactants, and the like. Thepigment having attached an electrophilic group may also be preparedusing the method described in PCT Publication No. WO 01/51566, which isincorporated in its entirety herein by reference.

The amount of electrophilic groups can be varied. Preferably, the totalamount of electrophilic groups is from about 0.01 to about 10.0micromoles of groups/m² surface area of pigment, as measured by nitrogenadsorption (BET method). For example, the amount of electrophilic groupsis from about 0.5 to about 4.0 micromoles/m². Additional attachedorganic groups which are not reactive with the thiol reagent may also beused.

The pigment having attached an electrophilic group may be purified bywashing, such as by filtration, centrifugation, or a combination of thetwo methods, to remove unreacted raw materials, byproduct salts andother reaction impurities. The pigments may also be isolated, forexample, by evaporation or it may be recovered by filtration and dryingusing known techniques to those skilled in the art. The pigment may alsobe dispersed into a liquid medium, and the resulting dispersions may bepurified or classified to remove impurities and other undesirable freespecies which can co-exist in the dispersion as a result of themanufacturing process. For example, the dispersion can be purified toremove any undesired free species, such as unreacted treating agentusing known techniques such as ultrafiltration/diafiltration, reverseosmosis, or ion exchange.

In one embodiment, the process of the present invention comprises thestep of combining a pigment having attached an electrophilic group and athiol reagent. In this first embodiment, the thiol reagent comprises atleast one —SH group and at least two ionic or ionizable groups. As usedherein, “at least one” and “at least two” refers to the stoichimetricamount of each group. Thus, for this first embodiment, the thiol reagenthas two ionic or ionizable groups for each —SH group. The thiol reagentcan be either an alkyl or aryl thiol that is substituted with at leasttwo ionic or ionizable groups. The amount of thiol reagent can be anyamount capable of reacting with the electrophilic groups on the pigment.Preferably, the ratio of the weight of the thiol reagent to the weightof the pigment is from about 0.1/1 to about 10/1 and more preferablyfrom about 0.2/1 to about 2/1.

An ionic group is either anionic or cationic and is associated with acounterion of the opposite charge including inorganic or organiccounterions such as Na⁺, K⁺, Li⁺, NH₄ ⁺, NR′₄ ⁺, acetate, NO₃ ⁻, SO₄ ⁻²,R′SO₃ ⁻, R′OSO₃ ⁻, OH⁻, and Cl⁻, where R′ represents hydrogen or anorganic group such as a substituted or unsubstituted aryl and/or alkylgroup. An ionizable group is one that is capable of forming an ionicgroup in the medium of use. Organic ionic groups include those describedin U.S. Pat. No. 5,698,016, the description of which is fullyincorporated herein by reference.

The thiol reagent may comprise at least two anionic of anionizablegroups. Anionic groups are negatively charged ionic groups that may begenerated from groups having ionizable substituents that can form anions(anionizable groups), such as acidic substituents. They may also be theanion in the salts of ionizable substituents.

Representative examples of anionic groups include —COO⁻, —SO₃ ⁻, —OSO₃⁻, —HPO₃ ⁻, —OPO₃ ⁻², and —PO₃ ⁻². Representative examples ofanionizable groups include —COOH, —SO₃H, —PO₃H₂, —R′SH, —R′OH, and—SO₂NHCOR′, where R′ represents hydrogen or an organic group such as asubstituted or unsubstituted aryl and/or alkyl group. Preferably, theanionic or anionizable group is a carboxylic acid group, a sulfonic acidgroup, or salts thereof. Thus, the thiol reagent can be an alkylthiolthat is substituted with at least two carboxylic acid groups, such as,for example, mercaptosuccinic acid.

The thiol reagent may comprise at least one cationic or cationizablegroup. Cationic groups are positively charged organic ionic groups thatmay be generated from ionizable substituents that can form cations(cationizable groups), such as protonated amines. For example, alkyl oraryl amines may be protonated in acidic media to form ammonium groups—NR′₂H⁺, where R′ represent an organic group such as a substituted orunsubstituted aryl and/or alkyl group. The thiol reagent may alsocomprise both an anionic or anionizable group and a cationic orcationizable group.

For this first embodiment, it is preferred that the pigment havingattached an electrophilic group and the thiol reagent are combined underconditions which form the thiolate of the thiol reagent. For example, itis preferred that the pigment and thiol reagent are combined underalkaline conditions, which form the thiolate and may assist in thereaction of the thiol reagent with the pigment. In addition, alkalineconditions may increase the solubility of the thiol reagent,particularly when the ionic or ionizable groups of the thiol reagent areanionic or anionizable groups. Thus, it is preferred that the pigmentand thiol reagent are combined at a pH greater than or equal to 7, morepreferably greater than or equal to 9, and most preferably greater thanor equal to 11.

In a second embodiment, the present invention comprises the step ofcombining, in any order, a pigment having attached an electrophilicgroup and a thiopolymer comprising at least one —SH group. The —SH groupmay be present along the backbone of the thiopolymer, such as, forexample, as part of a pendant group, or as a terminating group on theend(s) of the polymer. The thiopolymer preferably further comprises atleast one ionic or ionizable group. The ionic or ionizable groups may beany of those described above. Thus, the thiopolymer may be any polymercomprising at least one —SH group and at least one ionic or ionizablegroup. The amount of thiopolymer can be any amount capable of reactingwith the electrophilic groups on the pigment. Preferably, the ratio ofthe weight of thiopolymer to the weight of the pigment is from about0.1/1 to about 10/1, and more preferably from about 0.2/1 to about 2/1.

Preferably, the thiopolymer comprises the reaction product of a polymerhaving at least one reactive group, such as an anhydride, an activatedcarboxylic acid, or a carboxylic acid group or salt thereof, and asubstituted alkyl or aryl thiol, such as an aminoalkane thiol or anaromatic amino thiol. Preferably, the substituted alkyl or aryl thiol isaminoethane thiol.

Examples of polymers having at least one reactive group includeanhydride polymers, such as poly(styrene-maleic anhydride) andcarboxylic acid polymers, such as polyacrylic acid, polymethacrylicacid, and copolymers of acrylic or methacrylic acid, includingpoly(styrene-acrylic acid), poly(styrene-methacrylic acid),poly(ethylene-acrylic acid), or copolymers of acrylic and methacrylicacid with alkyl acrylates or methacrylates. Other suitable carboxylicacid polymers include polyesters, polyurethanes, and polyamides, whichhave carboxylic acid end groups. If needed to improve the reactivity ofthe carboxylic acid groups, an activating agent may optionally be added,thus forming a polymer having at least one activated carboxylic acid.The activated carboxylic acid may be a mixed anhydride, such as thatformed by the reaction of a carboxylic acid or salt with ethylchloroformate. Other activated carboxylic acid groups and activatingagents to prepare them will be known to one skilled in the art.

When the thiopolymer is the reaction product of a polymer having atleast one reactive group and a substituted alkyl or aryl thiol, theamount of each reagent need not be stoichiometric. For example, theamount of aminoalkyl or aromatic amino thiol may be less than the amountof the reactive group in the polymer. Any remaining reactive groups maybe further reacted. For example, when the resulting thiopolymer hasremaining anhydride groups, these may be further reacted with base, tohydrolyze the remaining anhydrides and form carboxylic acid groups, orsalts thereof. Alternatively, reagents such as alkyl or aryl amines andalcohols may be added to react with the remaining anhydride groups toform amic acids (or imides) and half acid esters, respectively. Thisresulting thiopolymer can then be used in the process of the presentinvention to be combined with a pigment having attached an electrophilicgroup.

For this second embodiment, the process of the present invention mayfurther comprise the step of adding an alkylating agent. The alkylatingagent is used to “cap” any thiol groups which remain after thethiopolymer and pigment having attached an electrophilic group have beencombined. Alkylating agents for thiol groups are known to one skilled inthe art and include, for example, alkyl halides, haloacetates or saltsthereof, or α,β-unsaturated carbonyl and sulfonyl compounds such asacrylates and methacrylates (including, for example, acrylic acid,methacrylic acid, or salts thereof), vinyl sulfonic acid or saltsthereof, and maleates (including, for example, maleic acid or saltsthereof, or maleimide).

The present invention further relates to a modified pigment. In oneembodiment, the modified pigment comprises a pigment having attached agroup comprising the formula —S—[PI]. The group PI represents an organicgroup substituted with at least two ionic or ionizable groups. Thepigment and ionic or ionizable groups may be any of those describedabove. For example, the group PI can represent an organic groupcomprising a branched or unbranched alkyl group substituted with atleast two ionic or ionizable groups, preferably at least two carboxylicacid groups. An example of a preferred group PI is a succinic acid groupor salt thereof.

The group PI may also represent a polymeric group comprising at leastone ionic or ionizable group. The ionic or ionizable groups may be anyof those described above. The polymeric group can be a homopolymer,copolymer, terpolymer, and/or a polymer containing any number ofdifferent repeating units. Further, the polymeric group can be a randompolymer, alternating polymer, graft polymer, block polymer, star-likepolymer, and/or comb-like polymer. Preferably, the polymeric groupcomprises a homopolymer or copolymer of acrylic acid, methacrylic acid,maleic acid, or salts thereof.

In a second embodiment, the modified pigment of the present inventioncomprises a pigment having attached a group comprising the formula—X-Sp-S—[PI]. X, which is directly attached to the pigment, representsan arylene or heteroarylene group or an alkylene group and issubstituted with an Sp group. Sp represents a spacer group. The group PIis as described above and can represent an organic group substitutedwith at least two ionic or ionizable groups or a polymeric groupcomprising at least one ionic or ionizable group.

The group Sp represents a spacer group which, as used herein, is a linkbetween two groups. The group Sp can be a bond or a chemical group.Examples of chemical groups include, but are not limited to, —O₂C—,—CO—, —COCH₂—, —COC₂H₄—, —OCOCH₂—, —OCOC₂H₄—, —NRCOCH₂—, —NRCOC₂H₄—,—OSO₂—, —SO₂—, —SO₂C₂H₄—, —SOC₂H₄—, —NRSO₂C₂H₄—, —S_(k)—, —NRCO—,—NRCOCH(CH₂CO₂R)—, —NRCOCH₂CH(CO₂R)—, —N(COR)(CO)—, imide groups(including maleimide groups), arylene groups, linear or branchedalkylene groups, and the like. R, which can be the same or different,represents hydrogen or an organic group such as a substituted orunsubstituted aryl or alkyl group, and k is an integer, such as from 1to 7.

The group X represents an arylene or heteroarylene group or an alkylenegroup. X is directly attached to the pigment and is further substitutedwith an Sp group. The aromatic group can be further substituted with anygroup, such as one or more alkyl groups or aryl groups. Preferably, thearylene group is phenylene, naphthylene, or biphenylene. When Xrepresents an alkylene group, examples include, but are not limited to,substituted or unsubstituted alkylene groups which may be branched orunbranched. The alkylene group can be substituted with one or moregroups, such as aromatic groups. Examples include, but are not limitedto, C₁-C₁₂ groups like methylene, ethylene, propylene, or butylene,groups. Preferably, X is an arylene group.

The group X may be substituted with one or more functional groups.Examples of functional groups include, but are not limited to, R″, OR″,COR″, COOR″, OCOR″, carboxylates, halogens, CN, NR″₂, SO₃H, sulfonates,sulfates, NR″(COR″), CONR″₂, NO₂, PO₃H₂, phosphonates, phosphates,N═NR″, SOR″, NSO₂R″, wherein R″ which can be the same or different, isindependently hydrogen, branched or unbranched C₁-C₂₀ substituted orunsubstituted, saturated or unsaturated hydrocarbons, e.g., alkyl,alkenyl, alkynyl, substituted or unsubstituted aryl, substituted orunsubstituted heteroaryl, substituted or unsubstituted alkaryl, orsubstituted or unsubstituted aralkyl.

As shown by the structure above, the group PI is attached to the pigmentthrough the spacer group Sp and a sulfur atom. However, it will also berecognized that, when the group PI is a polymeric group, the group PIcan also be attached to the pigment at multiple points along the polymerchain through proper choice of substituent groups on the repeatingmonomer units. These substituents may also comprise spacer groups or—X-Sp- groups as described above. Thus, these groups can be attached tothe pigment at either end or at points along the backbone.

For the modified pigments of the present invention, the amount ofattached groups can be varied. Preferably, the total amount of attachedgroups is from about 0.01 to about 10.0 micromoles of organic group/m²surface area of pigment, as measured by nitrogen adsorption (BETmethod). For example, the amount of attached groups is between fromabout 0.5 to about 4.0 micromoles/m². Additional attached groups, nothaving the formulas described above, may also be used. Furthermore, themodified pigments of the present invention may be purified using thetechniques and methods described above.

The modified pigments of the present invention can be used in a varietyof applications. For example, the modified pigments can be dispersed ina liquid vehicle and used in an ink or coating application. The vehiclecan be either an aqueous or non-aqueous vehicle, depending on the natureof the attached organic group. In particular, the modified pigments canbe used in an inkjet ink, such as an aqueous inkjet ink. Suitableadditives may be incorporated into these inkjet ink compositions toimpart a number of desired properties while maintaining the stability ofthe compositions. For example, surfactants may be added to furtherenhance the colloidal stability of the composition. Other additives arewell known in the art and include humectants, biocides, binders, dryingaccelerators, penetrants, dyes, buffers, and the like.

The present invention will be further clarified by the followingexamples which are intended to be only exemplary in nature.

EXAMPLES

For the following examples, the styrene-co-maleic acid polymers wereobtained from the Sartomer Company and are shown in Table 1:

TABLE 1 Polymer ID M_(W) Styrene:Maleic Anhydride Ratio SMA(1000) 5,5001:1 SMA(2000) 7,250 2:1 SMA(3000) 9,500 3:1 SMA(1440)* 7,500 1.5:1  *SMA(1440) polymer was prepared by reacting approximately 65% of theanhydrides of the SMA starting polymer with 2-butoxyethylalcohol toafford the corresponding half acid ester.

Dimethylformamide (DMF), acrylic acid, mercaptosuccinic acid (MEA),aminoethanethiol hydrochloride (AET.HCl), 5,5′-dithiobis(2-nitrobenzoiocacid) (DTNB), ethylchloroformate, concentrated HCl, and triethylamine(TEA) were obtained from Aldrich Chemical Co. and used without furtherpurification. Joncryl® 680 was obtained from S. C. Johnson.

Particle size was determined using a Microtrac® Particle Size Analyzer,and the values reported are the mean volume particle size (mV). Percentattached polymer was calculated from thermogravimentric analysis (TGA)using a TA Instruments TGA Model 2950. The samples were analyzed undernitrogen according to the following temperature profile: 10° C./min upto 110° C., hold at 110° C. for 10 minutes, continue heating at 10°C./min up to 800° C., and hold at 800° C. for 10 minutes. Percentattached material is determined from comparison of the weight lostbetween 110° C. and 800° C. of the final product compared to that of thestarting materials.

Examples 1-3

The following examples describe the preparation of a modified pigment ofthe present invention according to Scheme 1 below:

Example 1

A 14.9% aqueous dispersion of Black Pearls® 880 carbon black (availablefrom Cabot Corporation, Boston, Mass.) having attached a2-(sulfatoethylsulfone) group was prepared according to the proceduredescribed in PCT Publication No. WO 01/51566 to yield a pigmentdispersion. The resulting pigment having attached an electrophilic groupwas analyzed for sodium content to determine that the amount of attachedgroup was 0.3 mmol/g of dry carbon black.

A solution of 0.5 g (3.33 mmol) mercaptosuccinic acid in 5 ml ofdeionized water was mixed with 20 g of the above pigment dispersion in around bottom flask and the resultant mixture was stirred at roomtemperature, under an atmosphere of nitrogen. To this was added dropwise15 ml of 1N NaOH to afford a pH of 12.8 and then the mixture was stirredovernight to give a dispersion of a modified pigment.

The modified pigment dispersion was purified by diafiltration using apolysulfone hollow fiber membrane with a pore size of 0.05 microns. Thesolution was first concentrated to 35 ml and then diafiltered with 175ml 0.1M NaOH followed by 245 ml of deionized water. The final pH of thepermeate was between 6-7.

The resulting purified modified pigment dispersion had a particle sizeof 112 nm and a pH of 11.0. The modified carbon black pigment wasanalyzed for sodium and compared to the starting pigment having attachedan electrophilic group. Results are shown in Table 2 below.

Example 2

For this example, the procedure described in Example 1 was followed,with the exception that the dispersion of Black Pearls® 880 carbon blackhaving attached a 2-(sulfatoethylsulfone) group was replaced with a 5.7%solids dispersion of Pigment Yellow 74 (available from Sun Chemical)having the same attached electrophilic group, also prepared according tothe procedure described in WO 01/51560. Results from the Na+ analysis ofthis modified pigment are shown in Table 2 below.

Example 3

For this example, the procedure described in Example 1 was followed,with the exception that the dispersion of Black Pearls® 880 carbon blackhaving attached a 2-(sulfatoethylsulfone) group was replaced with a20.51% solids dispersion of Pigment Red 122 (available from SunChemical) having the same attached electrophilic group, also preparedaccording to the procedure described in WO 01/51560. Results from theNa+ analysis of this modified pigment are shown in Table 2 below.

TABLE 2 Example % Na % Na # Pigment before after 1 Black Pearls ® 8800.69 1.1 carbon black 2 Pigment Yellow 74 0.20 0.50 3 Pigment Red 1220.50 0.77

Examples 4-11

The following examples describe the preparation of anaminoethanethiolated-SMA (styrene-maleic anhydride) polymer andsubsequent modified pigment according to Scheme 2 below:

Aminoethanethiol is reacted in DMF with some or all of the anhydrides ofthe SMA polymer. The resulting product molecular weight and acid numberhave a direct correlation to the extent of this reaction. FIG. 1 andFIG. 2 show the expected dependence of molecular weight and acid numberon the targeted percentage of anhydrides reacted with aminoethane thiol.These are determined from the theoretical ratio of styrene/maleicanhydride in the starting polymer. For example, SMA(3000) has a 3/1ratio of styrene to maleic anhydride (from the manufacturer's productsheet). If 50% of the anhydride groups are targeted for reaction withAET.HCl, the expected acid number for the resulting product would beapproximately 190 and the expected MW would be approximately 10400.Thus, by targeting the percent of anhydrides reacted with the thiolreagent, the properties of the polymer and the subsequent modifiedpigment may be controlled.

Example 4

A solution was prepared by dissolving 20 g (0.049 mol anhydride) ofSMA(3000) in 100 ml of dry DMF. To this stirred solution, at roomtemperature, under a steady stream of nitrogen gas, was added 4.2 g(0.037 mol) of 2-aminoethanethiol hydrochloride as a solid in oneportion and then 5.2 ml (0.074 mol) triethylamine, dropwise. Theresultant mixture was heated at 45° C. for 30 minutes and then at roomtemperature for 4.5 hours. The product was isolated by slowly droppinginto vigorously stirred 1N HCl (600 ml). After the addition, the mixturewas stirred for another 60 minutes and then suction filtered, washedwith 400 ml of 1N HCl and then 400 ML of deionized water. The resultingproduct was briefly air dried to afford 61 g of a free flowing whitesolid which contained 62% moisture, as measured by weight loss afterheating at 110° C. for 1 hour.

The aminoethanethiolated-SMA polymer was dried at 110° C. Results fromelemental combustion analysis are shown in Table 3 below. Thiols weremeasured by titration with DTNB following a modification of Ellman'sprocedure (Ellman, G. L. (1958) Arch. Biochem. Biophys. 74, 443;Bioconjugate Techniques, Greg T. Hermanson, Academic Press, Inc.,copyright 1996, p 88). The resulting polymer was found to have 1.4 mmolthiols/g dry polymer.

Example 5

For this example, the procedure described for Example 4 was used, withthe differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 6

For this example, the procedure described for Example 4 was used, withthe differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 7

For this example, the procedure described for Example 4 was used, withthe differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 8

For this example, the procedure described for Example 4 was used, withthe differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below. Example 9

For this example, the procedure described for Example 4 was used, withthe differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

Example 10

For this example, the procedure described for Example 4 was used, withthe differences noted in Table 3. Results from the analysis of theresulting aminoethanethiolated-SMA are shown in Table 3 below.

TABLE 3 Ex. Anhydrides AET.HCl % S % S % N % N # Polymer (mol) (mol)(Theor.)* (Actual) (Theor.)* (Actual) 4 SMA(3000) 0.049 0.037 5.14 5.182.25 2.48 5 SMA(3000) 0.049 0.049 6.39 6.66 2.79 2.83 6 SMA(3000) 0.0490.021 3.12 3.07 1.36 1.65 7 SMA(2000) 0.065 0.065 8.12 8.46 3.55 3.33 8SMA(2000) 0.065 0.047 6.46 7.21 2.83 3.16 9 SMA(1000) 0.10 0.10 11.59.14 5.03 4.4 10 SMA(1440) 0.11 0.11 2.20 1.55 0.97 0.83 *Theoretical %S and % N are based on the theoretical Styrene/Maleic anhydride ratiosof the starting polymers.

Example 11

A solution of 145 ml of 1M NaOH was magnetically stirred in a roundbottom flask at room temperature while nitrogen gas was bubbled throughthe liquid for 10 minutes. To this was added 54.8 g of theaminoethanethiolated polymer of Example 4 (62% moisture content). Theresultant mixture was heated under nitrogen to 40-50° C. until a clearyellow solution was obtained.

The 14.9% aqueous dispersion of Black Pearls® 880 carbon black havingattached a 2-(sulfatoethylsulfone) group described in Example 1 (140 g)was added dropwise to the yellow polymer solution over approximately 5minutes. An additional 13 ml of 1N NaOH was added to raise the pH to12-13. The resultant mixture was then stirred at 40-50° C. for 3.5 hoursto give a dispersion of the modified pigment of the present invention.

A sodium acrylate solution was prepared by dissolving 7.5 ml acrylicacid into deionized water containing 11.7 g of NaCO₃. This solution wasadded to the modified pigment dispersion to “cap” any unreacted thiolgroups. Heating and stirring were continued for another 3 hours and themixture was then allowed to cool slowly to room temperature. Thedispersion of the resulting capped modified pigment was purified bydiafiltration as described in Example 1 to reach a final permeatepolymer concentration of <50 ppm (monitored by measuring the absorbanceof the permeate at 250 nm in a UV-VIS Spectrometer; the concentration ofpolymer is calculated from the known epsilon).

The capped modified pigment dispersion (11.6% solids, pH=10.15) wasfound to have a particle size of 120.4 nm and a sodium level of 1.3%(based on the dried carbon black solid). TGA analysis showed that theattached polymer accounted for 14% of the total weight.

Examples 12-13

The following examples describe the preparation of an aminothiolated-SAA(styrene-acrylic acid) polymer and subsequent modified pigment accordingto Scheme 3 below:

Example 12

To a magnetically stirred solution of 10 g styrene-co-acrylic acid,(Joncryl® 680: M_(w)=4,900, Acid Number=215) dissolved in 100 ml DMFunder a steady stream of nitrogen at room temperature was added 5.4 ml(0.039 mol) of triethylamine. To this was added 1.84 ml (0.019 mol) ofethylchloroformate. The solution became slightly warm with some gasevolution and cloudiness. The resultant mixture was stirred at roomtemperature for 40 minutes. A solution of 2.2 g (0.019 mol)aminoethanethiol hydrochloride and 2.7 ml (0.019 mol) triethylamine in50 ml DMF was added dropwise to this mixture over 15 minutes, and theresulting cloudy solution was stirred overnight. The product wasprecipitated by slowly dropping into a rapidly stirred solution of 1NHCl (250 ml). The resulting white precipitate was suction filtered,washed with cold 1N HCl, cold deionized water, and then air dried toafford a chalky white solid. A sample of this aminoethanethiolated SAApolymer was dried at 110° C. Elemental combustion analysis results wereas follows: 71.84% C; 7.53% H; 1.53% N; 3.01% S.

Example 13

A solution of 12.5 ml of 0.5 M NaOH was magnetically stirred at roomtemperature while nitrogen gas was bubbled through the liquid for 10minutes. To this was added 1 g of the aminoethanethiolated SAA polymerof Example 12. To the resulting solution was added 2.9 g of the 14.9%aqueous dispersion of Black Pearls® 880 carbon black having attached a2-(sulfatoethylsulfone) group described in Example 1. This gave a finalpH of 12.5. This solution was stirred under nitrogen gas overnight. Theresulting modified pigment was purified by diafiltration as described inExample 1 to give a dispersion having the following physical properties:pigment concentration: 9.0% (wt/wt); UPA mv=137 nm; % N=0.48%; %S=2.28%; % sulfate=0.35%. TGA analysis showed that the attached polymeraccounted for 6% of the total weight.

Examples 14-15

The following examples describe the preparation of anaminoethanethiolated-SMA (styrene-maleic anhydride) polymer additionallyfunctionalized with an alkylamine. In Example 14 the alkylamine isaminoethane sulfonic acid and in Example 15 the alkylamine is apolyamine (Jeffamine® XTJ506).

Example 14

To a 3-neck round bottom flask equipped with an overhead stirrer wasadded 1.5 liters of DMF followed by 300 g (0.735 mol anhydride) ofSMA(3000). The polymer suspension was heated to 40-50° C. to produce apolymer solution. The polymer solution was then de-oxygenated usingnitrogen. To this heated polymer solution under nitrogen was added 33.2g of aminoethanethiol hydrochloride (0.29 mol) and 45.9 g of aminoethanesulfonic acid (0.367 mol), and the mixture was stirred for an additional30 minutes at 40-50° C. Then 133 g of triethylamine (1.32 mol) was addeddropwise. The mixture was allowed to stir, coming to room temperature,overnight. The solution was then added dropwise into 7 liters of 1 MHCl. The resulting white solid was filtered, washed three times with 1liter of 1 M HCl and four times with 2 liters of DI-water, and thenair-dried. Elemental analyses showed that the product contained 2.13%nitrogen and 5.57% sulfur (theoretical values are 2.5% nitrogen and 6%sulfur).

Example 15

To a 3-neck round bottom flask equipped with an overhead stirrer wasadded 1.5 liters of DMF followed by 300 g (0.735 mol anhydride) ofSMA(3000). The polymer suspension was heated to 40-50° C. to produce apolymer solution. The polymer solution was then de-oxygenated usingnitrogen. To this heated polymer solution under nitrogen was added 41.5g of aminoethanethiol hydrochloride (0.355 mol) and 146 g of Jeffamine®XTJ506 (0.146 mol, available from Huntsman Corporation), and the mixturewas stirred for an additional 30 minutes at 40-50° C. Then 96 g oftriethylamine (0.95 mol) was added dropwise. The mixture was allowed tostir overnight at room temperature under a nitrogen blanket. Thesolution was then added dropwise into 7 liters of 1 M HCl. The resultingwhite solid was filtered, washed three times with 1 liter of 1 M HCl andfour times with 2 liters of DI-water, and then air-dried. Elementalanalyses showed that the product contained 1.21% nitrogen and 2.38%sulfur (theoretical values are 1.1% nitrogen and 2.48% sulfur).

Example 16

A solution of 100 mL of NaOH was magnetically stirred in a round bottomflask at room temperature while nitrogen gas was bubbled through theliquid for 10 minutes. To this was added 37 g of the SMA polymer ofExample 14 (46% moisture content). The resultant mixture was heatedunder nitrogen to 40-50° C. until a clear yellow solution was obtained.

A 10% aqueous dispersion of Black Pearls® 1100 carbon black havingattached a 2-(sulfatoethylsulfone) group (400 g), prepared according tothe procedure described in WO 01/51560, was added dropwise to the yellowpolymer solution over 10 minutes. An additional 25 mL of 1 M NaOH wasadded to raise the pH to 12-13. The reaction mixture was then stirred atroom temperature overnight to give a dispersion of the modified pigmentof the present invention.

To the dispersion was added 6.55 g of sodium acrylate to “cap” anyunreacted thiol groups. The mixture was allowed to stir for another 2hours at room temperature. The dispersion of the resulting cappedmodified pigment was purified by diafiltration as described in Example 1to reach a final permeate polymer concentration of <50 ppm (monitored bymeasuring the absorbance of the permeate at 250 nm in a UV-VISSpectrometer; the concentration of polymer is calculated from the knownepsilon).

The capped modified pigment dispersion (9.5% solids, pH 9.72) was foundto have a mean volume particle size of 108 nm and a sodium level of 2.5%(based on the dried carbon black solid). TGA analysis showed that theattached polymer accounted for 16% of the total solid weight.

Example 17

A solution of 280 mL of NaOH was magnetically stirred in a round bottomflask at room temperature while nitrogen gas was bubbled through theliquid for 10 minutes. To this was added 322 g of the SMA polymer ofExample 15 (69% moisture content). The resultant mixture was heatedunder nitrogen to 40-50° C. until a clear yellow solution was obtained.

The 10% aqueous dispersion of Black Pearls® 1100 carbon black havingattached a 2-(sulfatoethylsulfone) group (1000 g) used in Example 16 wasadded dropwise to the yellow polymer solution over 10 minutes. Anadditional 60 mL of 1 M NaOH was added to raise the pH to 12-13. Thereaction mixture was then stirred at room temperature overnight to givea dispersion of the modified pigment of the present invention.

To the dispersion was added 14 g of sodium acrylate to “cap” anyunreacted thiol groups. The mixture was allowed to stir for another 2hours at room temperature. The dispersion of the resulting cappedmodified pigment was purified by diafiltration as described in Example 1to reach a final permeate polymer concentration of <50 ppm (monitored bymeasuring the absorbance of the permeate at 250 nm in a UV-VISSpectrometer; the concentration of polymer is calculated from the knownepsilon).

The capped modified pigment dispersion (10.4% solids, pH=9.51) was foundto have a mean volume particle size of 78 nm and a sodium level of 1.3%(based on the dried carbon black solid). TGA analysis showed that theattached polymer accounted for 24% of the total solid weight.

1. A modified pigment comprising a pigment having attached a groupcomprising the formula —X-Sp-S—[PI], wherein X is an arylene,heteroarylene, or alkylene group, Sp is a spacer group, and PIrepresents a polymeric group comprising at least one ionic or ionizablegroup comprising the reaction product of a polymer having at least oneanhydride, at least one activated carboxylic acid, or at least onecarboxylic acid or salt thereof and an alkylamine, arylamine, oralcohol.
 2. The modified pigment of claim 1, wherein the alkylamine isaminoethane sulfonic acid or a polyamine.
 3. The modified pigment ofclaim 1, wherein the ionic or ionizable group is a carboxylic acidgroup, a sulfonic acid group, or a salt thereof.
 4. The modified pigmentof claim 1, wherein the polymeric group comprises a homopolymer orcopolymer of acrylic acid, methacrylic acid, maleic acid, or saltsthereof.
 5. The modified pigment product of claim 1, wherein the pigmentcomprises a blue pigment, a black pigment, a brown pigment, a cyanpigment, a green pigment, a white pigment, a violet pigment, a magentapigment, a red pigment, an orange pigment, a yellow pigment, or mixturesthereof.
 6. The modified pigment product of claim 1, wherein the blackpigment is carbon black.
 7. An ink composition comprising a) a liquidvehicle and b) the modified pigment of claim
 1. 8. The ink compositionof claim 7, wherein the ink composition is an inkjet ink composition.